Deirdre Jeter Biology II, 2013 Plants Deirdre Jeter Biology II, 2013

Plants Multicellular eukaryotes, cell walls (cellulose), most are autotrophs Use photosynthesis (chloroplasts); provides oxygen necessary for life Very diverse group Provide materials for buildings, paper, furniture, clothing, & medicines

Surviving on Land To survive on land plants have to be able to: Absorb nutrients from their surroundings Avoid dehydration/drying out Be able to disperse without using water

Surviving on Land, cont. 2 major groups: Nonvascular plants—no roots/vascular systems Vascular plants—have roots and vascular systems Fungi help plants absorb nutrients (mycorrhizae)

Surviving on Land, cont. Cuticle—waxy covering on outside of plants Makes it easier for plants to retain water Disperse using spores or seeds that can float on the wind or be carried by animals

Life Cycles Has alternation of generations Haploid gametophytes alternate with diploid sporophytes Zygotes divide through mitosis to produce sporophytes Diploid sporophytes produce haploid spores through meiosis

Life Cycles, cont. Spores grow into haploid gametophytes that produce haploid gametes through mitosis End first set of notes!

Nonvascular Plants Small plants that reproduce using spores Do not have true roots, stems, and leaves (vascular system)

Nonvascular Plants, cont. Water & nutrients transported by osmosis & diffusion Slow & only over small distances Limits the size of the plants

Mosses Most common nonvascular plants Green parts we recognize are gametophytes

Mosses, cont. Sporophytes grow from tips of gametophytes Are not green Have bare stalks topped by spore capsules (sporangia) Most have a cuticle, stomata (openings that allow gas exchange in plants), and simple conducting cells

Liverworts Like mosses, grow in mats of individual plants Have no stomata, cuticle, or conducting cells

Liverworts, cont. Some species have flat gametophytes with lobes Made of structures that resemble stems & leaves Sporophytes are very small & consist of a short stalk with a sporangium on top

Hornworts Like liverworts, have no conducting cells Sporophytes have stomata & a cuticle Hornlike; grow up from flat gametophytes

Nonvascular Plant Reproduction Like all plants, life cycles have an alternation of generations Gametophytes must be covered in water for fertilization to occur Gametophytes that produce eggs are archegonia Gametophytes that produce sperm are antheridia

Nonvascular Plant Reproduction, cont. Spores are produced by sporophytes in a sporangium Sporophytes are smaller than gametophytes Grow from gametophytes & depend on them for nutrients

Moss Life Cycle Diploid sporophytes produce haploid spores through meiosis Mature spores are released & spread by wind or water Spores settle to the ground & grow into haploid gametophytes

Moss Life Cycle, cont. Gametophytes produce eggs & sperm through mitosis When water covers mosses, sperm swim to nearby archegonia to fertilize eggs

Seedless Vascular Plants Do not produce seeds Sporophytes have vascular tissue; gametophytes do not Vascular systems allow them to develop true roots, stems, & leaves Grow much larger than nonvascular plants

Seedless Vascular Plants, cont. Gametophytes grow on or below surface of the soil Water required for fertilization 2 major groups: Lycophytes (club mosses) Monilophytes (ferns & related species)

Club Mosses Not true mosses because they have roots, stems, & leaves Stems branch from underground rhizome

Club Mosses, cont. Spores develop in sporangia that form on specialized leaves Some species form cones Clusters of non-green, spore-bearing leaves

Ferns & Related Species Most common seedless vascular plants Sporophytes are what we recognize as ferns Have a rhizome that is anchored by roots & leaves

Ferns & Related Species, cont. Leaves, called fronds, that have small sporangia that grow on their underside

Seedless Vascular Plant Reproduction Like nonvascular plants, must have water for fertilization to occur Sporophytes much larger than gametophytes Archegonia & antheridia develop on lower surface of gametophytes

Seedless Vascular Plant Reproduction, cont. Most species have egg & sperm produced by the same individual (has archegonia & antheridia) Some produce gametes in separate structures

Spores Haploid; produced by meiosis Capable of growing into an adult without fusing with another cell Has thickened walls that help prevent drying out & help withstand adverse conditions

Spores, cont. Form in sporangia Cluster of sporangia in ferns called a sorus Can be used to identify fern species End second set of notes

Seed Plants Vascular plants that produce seeds Development of seeds enhanced the survival & dispersal of offspring

Seed Plants, cont. 2 groups: Gymnosperms Angiosperms Seeds do not develop within a fruit Most develop within a cone Angiosperms Seeds develop within fruits (ripened ovary) Flowering plants

Reproduction in Seed Plants Does not require water Sporophyte is dominant; gametophyte is microscopic

Reproduction in Seed Plants, cont. Sporophytes produce 2 types of spores that produce 2 types of gametophytes Female gametophyte develops inside an ovule Male gametophyte develops inside a pollen grain

Reproduction in Seed Plants, cont. Pollination—the transfer of pollen grains from the male reproductive structures to the female reproductive structures Pollen tube grows into the female gametophyte & sperm passes directly to the egg for fertilization

Seeds Ovule that contains a fertilized embryo Outer ovule layers harden to form the seed coat Protects embryo from mechanical injury & harsh environment

Seeds, cont. Contain tissue that provides nutrients to embryos In gymnosperms, tissue forms from female gametophyte In angiosperms, tissue called endosperm

Seed Dispersal May prevent competition for water, nutrients, light, & living space Some seeds have wing-like structures so they can float on the wind Dandelion & milkweed seeds have parachute-like structures to help them drift

Seed Dispersal, cont. Some fruits have hooks that cling to animals’ fur Some fruits are food for animals Seeds dispersed through animals’ feces

Gymnosperms One of the most successful groups of plants 4 major groups: Conifers Cycads Ginkgoes Gnetophytes

Conifers Most familiar gymnosperms Needle-like leaves or leaves that are reduced to tiny scales Grow in cool, dry regions Pollen grains dispersed by wind

Cycads Short stems & palm-like leaves Cones that produce pollen & those that produce seeds develop on different plants Grow in tropical areas Pollen grains dispersed by insects

Ginkgoes Only living species is the maidenhair tree Fan-shaped leaves Male & female gametophytes develop on separate trees Seeds do not develop in a cone Pollen grains dispersed by wind

Gnetophytes Diverse group of trees, shrubs, & vines Produce seeds & pollen in cones

Conifer Life Cycle Diploid zygote develops when sperm fertilizes an egg Becomes dormant while seeds form Seeds are released when they mature & grow when conditions are favorable

Cones Whorls (circles) of modified leaves called scales Gametophytes of most gymnosperms develop inside cones Male (pollen) cones produce pollen grains Female (seed) cones produce ovules

Cones, cont. Many gymnosperms produce male & female cones on the same plant Female cones open for pollination, then close until seeds mature End 3rd set of notes

Angiosperms Divided into 2 groups: Monocots Seeds have 1 seed leaf (cotyledon) Long, narrow leaves with parallel veins Flowers with parts in multiples of 3

Angiosperms Dicots Seeds have 2 seed leaves Leaves with branching veins Flowers with parts in multiples of 4 or 5

Angiosperm Reproduction Occurs within flowers Specialized reproductive structures of angiosperms Promote pollination and fertilization more efficiently than cones

Flower Structure & Kinds of Flowers Arranged in 4 concentric whorls (circular swirls) Outermost whorl consists of the sepals Protect flowers from damage while they are buds

Flower Structure & Kinds of Flowers, cont. Second whorl consists of the petals Attract pollinators Third whorl consists of stamens Produce pollen in anthers

Flower Structure & Kinds of Flowers, cont. Fourth whorl consists of 1 or more pistils Produce ovules in ovaries (swollen lower portion of pistils) Complete flowers Have all 4 basic flower parts

Flower Structure & Kinds of Flowers, cont. Incomplete flowers Lack 1 or more of the basic flower parts

Angiosperm Life Cycle Sporophytes produce haploid spores through meiosis Spores form gametophytes Female gametophytes grow inside ovules Male gametophytes grow in anthers of stamens

Angiosperm Life Cycle, cont. Pollination occurs when pollen grain is moved from anther to stigma

Angiosperm Life Cycle, cont. Pollen tube grows into style to release 2 sperm into the ovule (double fertilization) 1 sperm fertilizes an egg The other joins with 2 haploid nuclei to form a triploid cell Develops into endosperm to provide nutrients for the embryo

Pollination 2 types of plants Self-fertilizers—fertilize their own ovules Cross-fertilizers—fertilized by pollen from other plants

Pollination, cont. Cross-fertilizing plants adapted for pollination by wind or animals Strong odors, bright colors, nectar, or shapes used to attract animals Wind-pollinated plants small without bright colors, strong odors, or nectar

Fruits The ovary of a plant after fertilization Help to protect developing seeds Primary function is seed dispersal Eaten by animals Structures for wind dispersal Some plants forcefully eject their seeds

Vegetative Reproduction Asexual reproduction involving non-reproductive parts (stems, roots, leaves) Occurs through modified stems, such as bulbs, tubers, and stolons Faster than sexual reproduction Allows single plants to rapidly populate an area